Ships are a primary means of transporting relief supplies. Cargoes vary from supplies of food, water and medicines, to bedding, shelter and heavy machinery.

The main problem with delivering aid by ship is that it takes time to arrive. However, vessels already at sea can be quickly diverted to emergency areas.

The scale of the tsunami disaster has seen a number of military ships joining the aid effort. They include 34 ships from the Indian navy and the US aircraft carrier Abraham Lincoln with its four accompanying ships.

The WFP is considering using shallow-draught military landing barges to deliver supplies directly to local communities, reducing pressure on stretched or tsunami-damaged harbour facilities.

Otherwise helicopters are useful in ferrying supplies from ships to shore.